Here is a link that helped me a bit. You need new timing chains (primary and secondary), the timing chain crank sprocket, and the intake cams and all four cam phasers to make the 2015 engine work in the 2011-2014 Mustang GTs. The PCM is not compatible with the 2015+ intake mainfold charge motion generator/thing, or the midlock phasers or intake cams. Everything I've seen suggest the valves being larger doesn't pose an issue. I hope you get everything ironed out. https://performanceparts.ford.com/download/PDFS/FPP_Gen_2_Coyote_Technical_Reference_2-16.pdf You're using the 2011 intake manifold?